428 TOWER, DARWINISM. 
these examples of mimetic and protective resemblances. The only 
escape from the conclusion that Natural Selection had nothing to 
do with these phenomena is by added assumption, as, for example, 
that Natural Selection acted in past time but is no longer operative. 
This is an illogical assumption to make, because it is contrary to 
the principle of the uniform action of natural forces and also 
involves the unanswerable question of why the process operated 
in the past but is not found to be operating in the present. I know 
of no answer; there is a sufficiency of plausible explanations, so 
the only deduction possible is that while Natural Selection furnishes 
a plausible hypothesis in explanation of these cases, there is no 
evidence that the hypothetical activities are realities in nature, 
Consequently, to be scientifically honest, it is necessary to admit. 
that there is no evidence in support of any hypothesis concerning 
the origin and production of these supposedly protected forms, 
nor even that they are protected at all. 
The entire topic ot protective form, coloration, mimicry and so 
on, as far as | have been able to observe it in the American 
tropics, is much more obvious and real when we are examining 
specimens in a museum than it is when we encounter these 
specimens in their natural habitats. Protective adaptation is one 
of the bulwarks of the Natural Selectionists and appears more 
often as an illustrative example of the operation of Natural Selection 
than does any other phenomenon pertaining to organisms. In 
many respects these protective resemblances provide a crucial 
test of the Hypothesis of Natural Selection, because, while many 
other organic phenomena can conceivably be explained upon more 
than one hypothesis, these alleged highly adaptive protective devices 
thusfar seem explicable only on the basis of Natural Selection. 
ELIMINATION BY PHYSICAL ENVIRONMENT. 
Abundant speculations exist concerning the action of physical 
factors of the environment in Natural Selective effects, but relatively 
few of these conjectures are based upon adequate observations. 
The observations of WELDON on the crabs in Plymouth Harbor, 
those of Bumpus on the sparrows killed in New York as the. 
result of a severe. storm are interesting, suggestive and indicate 


